There are many articles of manufacture that have plastic tubes joined to flexible plastic sheets. For example, many products are packaged in plastic wrap which, because of the shapes of the products, dictate that the packages have tubular extensions. Other flexible containers are in the form of tubes with end flanges. Asbestos abatement containers fall in this category. For example, U.S. Pat. No. 4,852,687 illustrates a plastic enclosure for collecting asbestos as it is stripped from a ceiling. The enclosure has a funnel like enclosure from which a chute depends. Glove bags that are wrapped about asbestos clad pipes also have one or more tubes that depend from a shroud. Examples of these are shown in U.S. Pat. Nos. 5,553,933 and 5,632,846. Intravenous drip tubes used in medical facilities to meter fluids slowly into patients also have fitment tubes joined to pouches that are suspended from stands.
Plastic tubes can be and often are joined to plastic sheet materials with adhesives and with tapes. However, for speed and consistency, more often they are heat sealed which causes the plastics to fuse and provide a watertight or airtight joint. Heretofore this has commonly been done as shown in FIGS. 1-5 of the drawing. A plastic tube 10 is inserted through a tubular mandrel or anvil 12 having an annular step 13 in one end as shown in FIG. 1. An end of the tube is folded outwardly over the end of the mandrel as shown in FIG. 2 to form an annular tube lip 14. A plastic sheet 15 is positioned over the mandrel and tube lip as shown in FIG. 4. A sealing platen then presses the sheet against the tube lip 14 and the contiguous annular portion Of the tube that overlays the mandrel step. The platen is sometimes in the shape of a donut as shown at 17 in FIG. 3 or other times it is a disc as shown at 18 in FIG. 4. The sheet can have a precut hole or the hole can be formed in the sheet with an annular, electric cutting wire 19 affixed to the platen 18 as shown in FIG. 4. The sheet is then fused to the tube lip with heat generated by unshown electric heating elements in the mandrel or platen. The bonded tube and sheet are then removed as shown in FIG. 5.
A persistent problem with the just described method is that it produces pinholes in the seal that cause capillary leaks. This is due to the fact that the stretching of the tube end over the mandrel causes it to gather and wrinkle as indicated in FIGS. 2-4. Once these wrinkles are pressed against the flat sheet, radiating capillary channels are formed as the two layers are sealed.
Accordingly, it is seen that a need has long existed for a method of joining a plastic tube to a flexible plastic sheet in a manner that provides an air impervious annular seal that is substantially free of capillary leaks. It is to the provision of such therefore that the present invention is primarily directed.